Submitted by
Gard on Sat, 2003-11-08 03:11.
Quake 2
Using Clip Brushes - Richard Neff and David Hyde
One of the signs of a quality map maker for any game is creating maps that do two things:
- Create visually exciting areas for the player
- Create a level that is interesting to play
This tutorial is going to concentrate on the latter concept. More
precisely, the use of Clip brushes to help keep the player from being
"snagged" on small brushes used to help with the first concept above.
"Oh no! I'm stuck"
One of the things you'll notice if you fire up any of Id
Software's original Quake 2 levels, is that there are a lot of columns
and uneven surfaces running along walls. This creates an exciting
visual impact, however, you should notice that the player can run along
those walls backwards and not stop until they reach another wall.
To be more precise, let's look at the following screenshot from
one of those levels, base1.bsp (the first level in single player.)
Towards the end of the level, you'll see this wall near the stairs.
Note that there are both columns and light fixtures running along this
wall. Yet, if you press yourself against this wall and run all the way
to the next wall, you don't get "snagged." A very useful thing when you're being pursued by a Quake 2 monster, or worse yet, a real live Deathmatch opponent!
So, how is this done?
Ok, the answer is pretty obvious given the title - It was done
using Clip brushes. But, in this tutorial we'll look at the two
methods of using Clip brushes to keep players from being "snagged" while
playing your levels.
Clip brushes themselves are pretty easy to create. Simply create
a brush with the Clip texture on all sides of the brush. It's totally
invisible in the game and it won't have any effect on the poly count
(r_speeds) of the level. Essentially, they're like invisible "force
fields" that prevent the player from getting to an area (useful for more
than "snagging" problems also.) Some editors may require that you
manually specify the Clip content property, but most will automatically
create the Clip brush. If you run your map and see the Clip texture,
then you probably haven't applied that texture to all sides of the
brush.
The Two Techniques
Truthfully, none of this is rocket science - it's pretty
straightforward. However, there are two ways to handle not getting
"snagged." Consider the image above showing base1.bsp. One way to
help the player from getting snagged is to put an angled brush on both
sides of the columns or lights. For example, here's a screenshot in my
editor of a light fixture that hangs on a wall:
In this example, you'll notice that the clip brushes on each side are
designed to gently let the player get around the protruding light
fixture by forcing them along an angle between the wall and the fixture
itself. The slope of the angle is something you sometimes have to work
with, but typically a 45 degree angle between perpendicular surfaces
works well.
So, what's the drawback to this method? Two primary drawbacks
come to mind. One involves the player, the other often involves you,
the editor. First, if a player is running on the surface of a such a
wall, their direction will change slightly. For those players that
like to run backwards against a wall while firing, this will affect
those shots when the light fixture is hit. And, as well all know, this
could mean life or death in a deathmatch game!
The next drawback is with editing. If you wanted to do this
along a wall with a lot of columns or light fixtures, you'd have to
create 2 clip brushes for each object that protrudes from that wall.
Needless to say, this makes an already tedious process more painstaking!
So, this method is best used for any light fixtures or the like that
you've created as a prefab in your editor.
So, what's the easiest way to handle a wall like the base1.bsp
figure that won't take a lot of time to create, yet still allow the
player good movement along the wall? The answer is actually quite
simple -- make a Clip brush that covers all the protruding objects along
that wall. (And what Id actually did in that particular area.)
Here's some screenshots to help you out:
In this figure, here's a room with some columns
If the player were to run along the wall on the right, they'd get
snagged on every column and I'd need to make 6 total clip brushes using
the first technique.
However, if I make the Clip brush (the red box) like so:
Then, the player will run along the entire wall without getting
snagged or being moved. Plus, the added benefit to the level maker is
that it is a much simpler job to create 1 rectangular brush than 6
triangular ones!
So, why not use this method all the time? Well, one word --
doors. If we had a door on the right side we couldn't have the Clip
brush covering the door, the player would never be able to pass through
the door. In this case, a combination of the above methods would need
to be used.
Pretty Simple Huh?
Well, that's pretty much the main points about Clip brushes.
See, that wasn't very hard, was it? However, putting Clip brushes in
your level will make a big difference for those people playing your maps
(especially if you're designing DM or CTF maps.) So, it's worth the
extra time placing Clip brushes in your level.